The field of the disclosure relates generally to flexible alternating current transmission systems (FACTS) and, more particularly, to gas tube-switched FACTS and methods of use.
Many known electrical loads include both real and reactive components. For example, and without limitation, an electric motor is an inductive load, where an induction coil is energized to turn a rotor. Real power facilitates performance of work, such as driving a mechanical load on the electric motor, while reactive power facilitates storage of power due to a phase difference between transmitted voltage and transmitted current. Real power, P, is generally expressed in Watts. Reactive power, Q, is generally expressed in voltage-ampere reactive (var). Apparent power is a vector sum of real and reactive power, and is calculable as a product of a circuit's voltage and current. Apparent power, S, is accordingly expressed in voltage-amperes (VA).
Known power transmission systems deliver electrical power to electrical loads over transmission lines. The quality of the delivered power is characterized by a power factor, which is defined as a ratio of real power to apparent power, i.e., P:S. For purely resistive loads, the power factor is one, i.e., 1:1. For purely reactive loads, the power factor is zero, i.e., 0:1. Low power factors generally indicate inefficient power transmission, as the accompanying reactive load demands increased apparent power to achieve a demanded real power, resulting in increased heat loss due to increased current levels. Conversely, too little reactive power in a transmission system can degrade performance of transformers and transmission lines, resulting in poor voltage regulation, lower margins to voltage collapse, or poor power flow.
Some known power transmission systems include one or more var compensators to improve power transmission quality and efficiency by supplying additional reactive power to the system, thereby improving power factor, voltage regulation, voltage stability, and power flow. Known var compensators typically include an inductance or a capacitance that is coupled to the transmission line through one or more switches. The inductance or capacitance in some known var compensators includes a fixed passive capacitor or inductor. In other known var compensators, the inductance or capacitance includes power electronic devices or a combination of fixed passive devices and power electronics. When connected and energized, the inductance operates as a reactive current source and the capacitance operates as a reactive voltage source. In high voltage power transmission systems, var compensators typically utilize numerous devices in series to achieve the desired effect. Similarly, var compensators for high voltage power transmission systems generally require a transformer to interface between the transmission lines and the various devices of the var compensator. Consequently, selecting a var compensator for a given power transmission system typically includes a balance of high blocking voltage, low conduction losses, and low switching losses.